The present invention relates to a graphite sheet having anisotropy of physical properties, and a method for manufacturing the graphite sheet.
As graphite sheets, ones formed by stretching a mixture of a graphite powder and a binder resin, or by stretching expanded graphite into a sheet shape are known. Japanese Examined Patent Publication No. 1-49642 discloses a method for manufacturing a graphite sheet having flexibility by a thermal treatment and a rolling treatment of a polyimide film being a polymer film. Graphite sheets have an electric conductivity and a thermal conductivity excellent in the direction along the sheet surface, i.e. in the in-plane direction. The graphite sheet obtained by baking a polyimide film has properties of being highly flexible and hardly foldable.
In semiconductor packages for which the tendency of size reduction and thickness reduction accelerates and electronic devices for which function enhancement and performance enhancement progresses, the generated heat amount of exothermic bodies such as mounted devices and electronic components increases, and the exothermic bodies are highly densely mounted. Hence, technologies to effectively diffuse heat from exothermic bodies are demanded. However, conventional graphite sheets cannot sufficiently satisfy such a requirement.